In the related art, various techniques for discharging a small amount of liquid materials in a droplet shape through a discharging port by using a reciprocating plunger have been proposed.
For example, in a material distribution apparatus which distributes a small amount of liquid materials, an embodiment of PTL 1 discloses a configuration of an apparatus which introduces compressed air into an air chamber, moves a valve head away from a valve seat to open a valve, ejects the compressed air of the air chamber outward, causes a compression spring to press the valve against the valve seat, allows a shaft to generate a closing force and distributes the liquid material through an outlet end of a nozzle.
PTL 2 relating to the present applicant discloses a droplet discharge method in which a discharging port is opened by a rearward movement operation of a plunger rod using air pressure and a droplet is discharged through the discharging port by a forward movement operation of the plunger rod using an elastic force of a spring or the air pressure.
In a viscous fluid discharge apparatus, PTL 3 discloses a discharge apparatus that includes a cylindrical body which is formed in a cylindrical shape and has a viscous fluid containing chamber for containing a viscous fluid in a cylinder; a plunger which is inserted into the viscous fluid containing chamber and extrudes the viscous fluid; a piezoelectric driver which drives the plunger against a biasing force generated by a coil spring biasing the plunger in a direction opposite to a discharging direction of the viscous fluid; and a nozzle which is disposed in the cylindrical body to oppose the plunger and has a discharging port for discharging the viscous fluid.
PTL 4 relating to the present applicant discloses a droplet discharge apparatus that includes a plunger position determination mechanism which determines a position of a front end portion of a plunger when the plunger moves forward and stops in the vicinity of an inner wall of a liquid chamber located in a forward movement direction thereof.